Toggle overshot

ABSTRACT

An overshot includes a sleeve. A coupling member having a latched state and an unlatched state is disposed at a first end of the sleeve. A load-responsive toggle mechanism for alternating the coupling member between the latched state and the unlatched state is disposed at a second end of the sleeve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No. 61/040,981 filed Mar. 31, 2008.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a wireline overshot for connecting a wireline to an article within a borehole (or within a downhole tool in the borehole) and/or for retrieving an article from a borehole (or from a downhole tool disposed in the borehole).

2. Related Art

A “wireline” overshot is used to connect a wireline to an article within a drill string. The article can be, but need not be limited to, a wireline coring inner barrel, a soft material sampling tool, a data gathering assembly, or an optional portion of a downhole drilling assembly. The wireline overshot may also be referred to as a fishing tool. In one example, the wireline overshot connects to the article within the drill string by latching over a spearhead coupled to the article. In another example, the wireline overshot may latch onto the article within the drill string by engaging a circular (or receiving) portion of the article. The wireline is commonly a flexible wire rope but may also be a solid wire (or “slickline”), synthetic braided rope, or small-diameter, flexible tubing. The wireline is typically lowered and raised by a winch.

In a typical core barrel retrieval operation, a wireline overshot is lowered on the end of a wireline down the drill string, where it latches onto an inner tube assembly of a core barrel disposed within the drill string. The wireline overshot is then pulled back to the surface with the attached inner tube assembly. At the drill floor, the inner tube assembly is held in a clamp or lowered onto the drill floor. An operator releases the wireline overshot from the inner tube assembly manually and sets the wireline overshot aside. In cases where the wireline overshot needs to be unlatched from the inner tube assembly while still within the drill string, the method of unlatching the wireline overshot is commonly one of free-falling a release sleeve onto the wireline overshot, tensioning and releasing the wireline to ratchet a release pall, and repeated pulling or releasing of the wireline to shear a release pin. All of these operations require the wireline overshot to be reconfigured or rebuilt at the surface before it can function as an overshot again.

SUMMARY

In a first aspect of the invention, an overshot comprises a sleeve, a coupling member having a latched state and an unlatched state disposed at a first end of the sleeve, and a load-responsive toggle mechanism for alternating the coupling member between the latched state and the unlatched state disposed at a second end of the sleeve.

In a second aspect of the invention, an overshot comprises an outer sleeve and a coupling member disposed a first end of the outer sleeve. A first rotator is disposed within the outer sleeve and configured to alternately engage and disengage from the coupling member, thereby toggling the coupling member between an unlatched state and a latched state. A second rotator is disposed within the outer sleeve and configured to selectively displace and rotate the first rotator in response to an applied load. A weight member is disposed at a second end of the outer sleeve for applying a load to the second rotator.

In a third aspect of the invention, a method of connecting or disconnecting a wireline from an article comprises providing an overshot comprising a sleeve, a coupling member having a latched state and an unlatched state disposed at a first end of the sleeve, and a load-responsive mechanism for alternating the coupling member between the latched state and the unlatched state disposed at a second end of the sleeve. The method includes coupling a wireline to the load-responsive mechanism, aligning the article with the coupling member, and selectively activating the load-responsive mechanism to alternate the coupling member between the latched state where it engages the article and the unlatched state where it disengages from the article.

Other aspects of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, described below, illustrate typical embodiments of the invention and are not to be considered limiting of the scope of the invention, for the invention may admit to other equally effective embodiments. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

FIG. 1 is a cross-section of an overshot.

FIG. 2 is a cross-section of a toggle portion of the overshot of FIG. 1.

FIG. 3 shows the overshot of FIG. 1 positioned atop an inner tube assembly.

FIG. 4 shows a weight jar assembly of the overshot of FIG. 1 applying a load to an upper rotator of the overshot of FIG. 1 while the overshot is in an unlatched state.

FIG. 5 shows the upper rotator of FIG. 4 pushing down on a lower rotator of the overshot of FIG. 1.

FIG. 6 shows keys on the lower rotator of FIG. 5 sliding into key slots on a key holder sleeve of the overshot of FIG. 1.

FIG. 7 shows the lifting dogs latching onto a spearhead at the top of the inner tube assembly of FIG. 2.

FIG. 8 shows a weight jar assembly of the overshot of FIG. 1 applying a load to an upper rotator of the overshot of FIG. 1 while the overshot is in the latched state.

FIG. 9 shows the keys of the lower rotator of the overshot of FIG. 1 released from the key slots of the key holder sleeve of the overshot of FIG. 1.

FIG. 10 shows the overshot of FIG. 1 suspended at the end of a wireline.

FIG. 11 shows the overshot of FIG. 1 after it has engaged an inner tube assembly within a drill string and has been retrieved to the surface with the inner tube assembly.

DETAILED DESCRIPTION

FIG. 1 is a cross-section of an overshot 10 for connecting a wireline to an article. The overshot 10 includes a cap 60 for connection to a wireline. A weight jar assembly 44 is coupled to the cap 60. The weight jar assembly 44 may include a weight bar 19 attached to the cap 60 by fasteners 21, e.g., thread-and-set screws, and a jar stem 23 attached to the weight bar 19 by fasteners 25, e.g., thread-and-set screws. The jar stem 23 is received in a sleeve 22 and retained in the sleeve 22 by a jar bushing 27 mounted at the upper end of the sleeve 22. A toggle head 13 is received in the sleeve 22 and is positioned below the jar stem 23. A coupling member 14 is coupled to the toggle head 13 for engaging an article of interest. The article of interest may be any tool requiring a releasable connection with a wireline. For example, the article may be an inner tube assembly used to collect core samples from a subsurface formation, a soft material sampling tool, a data gathering assembly, and a component of a downhole drilling assembly. Connection and release of the overshot 10 from the article can be made at the surface, within a borehole, or within a tool disposed in the borehole.

For the purpose of engaging an article of interest, the coupling member 14 is configured to mate with a coupling member on the article of interest, or vice versa. The coupling member 14 and the coupling member on the article of interest may have several different configurations suited for the intended purposes. In the example shown in FIG. 1, the coupling member 14 is a latch having a pair of lifting dogs 18. A “lifting dog” is an elongated member having one end terminating in a hook for engaging a part. In the example shown in FIG. 3, the coupling member 14 is aligned to engage a coupling member 16 on an article 12. In this example, the coupling member 16 is a spearhead. Also, the article 12 is an inner tube assembly latched into a core barrel 56. However, as previously noted, the article 12 need not be limited to an inner tube assembly. The lifting dogs 18 can be manipulated, as will be described below, to toggle the coupling member 16 between a latched state where the lifting dogs 18 engage the spearhead 16 to an unlatched state where the lifting dogs 18 disengage from the spearhead 16. It should be noted that the coupling members 14, 16 may have different configurations than those shown in FIG. 3. For example, the coupling member 14 may be the spearhead while the coupling member 16 is the latch configured to engage with and disengage from the spearhead. In yet another example, one of the coupling members 14,16 may be a latch and the other of the coupling members 14,16 may be a receptacle for receiving the latch, wherein the receptacle includes a surface for retaining the latch.

Returning to FIG. 1, the lifting dogs 18 are pivotally coupled to an axle 26 of the toggle head 13. A spring 28 is disposed between the upper ends 30 of the lifting dogs 18 to bias the upper ends 30 of the lifting dogs 18 away from each other. The pivot joint 33 between the lifting dogs 18 causes the lower ends 32 of the lifting dogs 18 (which include the hooks for engaging a part) to be biased in a reverse direction to the upper ends 30 of the lifting dogs 18. A toggle mechanism for moving the lifting dogs 18 between the latched and unlatched states includes a lower rotator 34. In the unlatched state, the upper ends 30 of the lifting dogs 18 are received within a bore of the lower rotator 34 so that the wall of the lower rotator 34 acts as a restraining ring around the upper ends 30 of the lifting dogs 18. In this unlatched state, the upper ends 30 of the lifting dogs 18 are forced towards each other against the force of the spring 28 and the lower ends 32 of the lifting dogs 18 are forced away from each other. The lower rotator 34 is axially movable along the toggle head 13 and sleeve 22. To transition the overshot 10 to a latched state, the lower rotator 34 is moved a sufficient distance in an upward direction to release the upper ends 30 of the lifting dogs 18 from the lower rotator 34. Once the upper ends 30 are released, the spring 28 would move the upper ends 30 away from each other, thereby causing the lower ends 32 of the lifting dogs 18 to move towards each other and latch onto the spearhead 16, as will be further described below. The shaft 24 of the toggle head 13 includes a flange 36, and a spring 38 is arranged between an upper end 39 of the lower rotator 34 and the flange 36 to hold the lower rotator 34 in place about the shaft 24. The shaft 24 is coupled to the axle 26 to which the lifting dogs 18 are pivotally mounted.

The toggle mechanism includes an upper rotator 40 disposed about the shaft 24. The upper rotator 40 is held in place above the lower rotator 34 (and about the shaft 24) by a spring 42. The term “rotator,” as used herein and above, means a part that can rotate or that can rotate another part. In one example, the upper rotator 40 is configured to rotate the lower rotator 34. The upper rotator 40 is slidable along the shaft 24 upon application of a load to the upper rotator 40 by the weight jar assembly 44. For the upper rotator 40 to be slidable, the load applied by the weight jar assembly 44 must be sufficient to overcome the biasing force of the spring 42 holding the upper rotator 40 in place. As will be further explained below, the load should also be sufficient to overcome the biasing force of the spring 38 holding up the lower rotator 34, or the biasing force of the spring 38 holding up the lower rotator 34 should be less than that of the spring 42 holding up the upper rotator 40. A wireline (not shown) coupled to the weight bar 19 through the cap 60 is used to control the position of the jar stem 23 (of the weight jar assembly 44) within the sleeve 22. The jar stem 23 is movable between an upper position limited by the jar bushing 27 (at the upper end of the sleeve 22) and a lower position limited by the upper rotator 40. When the weight jar assembly 44 rests on the upper rotator 40, it applies a load to the upper rotator 40. As will be explained below, this load assists in shifting the lifting dogs 18 between the latched and unlatched states. Contact is required between the jar stem 23 and the upper rotator 40 to allow the weight jar assembly 44 to apply a load to the upper rotator 40. Contact can be achieved in one of two ways. One way is by letting go of tension in the wireline (not shown) coupled to the weight bar 19 so that the jar stem 23 slides down the shaft 24 to contact the upper rotator 40. The other way is by moving the overshot 10 upwardly so that the upper rotator 40 slides up the shaft 24 to contact the jar stem 23. A jar bushing 51 is disposed within the sleeve 22 and locked to the sleeve 22 by fasteners 53. A key holder sleeve 46 is mounted inside the sleeve 22 and attached to the jar bushing 51. The key holder sleeve 46 is generally concentric with the upper rotator 40, the lower rotator 34, and the shaft 24. The jar stem 23 is sized to slide through the jar bushing 51 into the key holder sleeve 46 as needed to contact the upper rotator 40. The jar stem 23 includes a bore 47 which fits over the shaft 24, thereby allowing the jar stem 23 to travel along the shaft 24.

In FIG. 2, the key holder sleeve 46 includes a plurality of keys 48. Some of the keys 48 are shortened to define a plurality of key slots 50. Stop pins 52 are inserted into the ends of some of the keys 48, resulting in a portion of the key slots 50 having stop pins 52 and a portion of the key slots 50 not having stop pins 52. A plurality of keys 54 is fastened to the lower rotator 34. The keys 54 are shaped to slide into the key slots 50 when aligned with the key slots 50. The stop pins 52 act to restrict the upward motion of the keys 54 when the keys 54 are received in the portion of the key slots 50 containing stop pins 52. In the example shown in FIG. 2, the keys 48, 54 have tapered ends 49, 55, respectively. When the weight of the upper rotator (40 in FIG. 1) is applied to the lower rotator 34, the tapered ends 49, 55 along with the force of the spring (38 in FIG. 1) rotate the lower rotator 34 for alignment from one slot to halfway to the next slot on the left. When the weight of the upper rotator (40 in FIG. 1) is lifted by the spring (42 in FIG. 1), the lower rotator 34 completes its rotation into the next slot.

FIG. 3 shows the overshot 10 positioned on top of an inner tube assembly 12 latched into a core barrel 56. The overshot 10 is in an unlatched state, with the lifting dogs 18 slid down the spearhead 16 and held open by the shoulder 57 of the spearhead 16. This frees the lower rotator 34 to rotate without the friction that would be caused by the spring 38. In the example shown in FIG. 3, tension in the wireline has been relaxed, allowing the weight jar assembly 44 to rest on and apply a load to the upper rotator 40. Relative motion between the overshot 10 and the wireline (not shown) is used to bring the jar stem 23 of the weight jar assembly 44 in contact with the upper rotator 40. Relative motion can be achieved by releasing the weight jar assembly 44 from above, e.g., through relaxation of tension in the wireline coupled to the weight jar assembly 44, or by moving the overshot 10 upwardly. The weight jar assembly 44 applies weight to the upper rotator 40 and, as shown in FIG. 4, causes the upper rotator 40 to slide down the key holder sleeve 46 and engage the lower rotator 34. As shown in FIG. 5, the upper rotator 40 pushes the lower rotator 34 down until the keys 54 (on the lower rotator 34) are positioned below the keys 48 (on the key holder sleeve 46). As previously explained, the load applied by the weight jar assembly (44 in FIG. 1) must be sufficient to overcome the force of the spring (42 in FIG. 1) holding up the upper rotator 40 and the force of the spring (38 in FIG. 1) holding up the lower rotator 34. The lower rotator 34 then rotates clockwise (looking down) as the tension of the spring (38 in FIG. 1) pushes the lower rotator 34 upwardly against the beveled surface 62 of the upper rotator 40. The keys 54 slide into the key slots 50 without the stop pins 52, as shown in FIG. 6. The lower rotator 34 moves upwardly as the keys 54 slide upwardly inside the key slots 50. As shown in FIG. 7, this causes the upper ends 30 of the lifting dogs 18 to be released from the lower rotator 34. The spring 28 moves the upper ends 30 of the lifting dogs 18 outwardly, which causes the lower ends 32 of the lifting dogs 18 to move inwardly and latch onto the spearhead 16. In the latched state, the weight jar assembly 44 is held again in tension to avoid exerting weight on the upper rotator 40, and the upper rotator 40 is held above the lower rotator 34 by the spring 42. The lower rotator 34 is held in place by the keyed connection described above and the force of the spring 38.

To release the lifting dogs 18 from the spearhead 16, the weight jar assembly 44 is again brought into contact with the upper rotator 40 to apply a load to the upper rotator 40, as shown in FIG. 8. As previously explained, the weight jar assembly 44 can either slide down to contact the upper rotator 40, or the overshot 10 can be moved upwardly to allow the upper rotator 40 to slide up and contact the weight jar assembly 44. The upper rotator 40, under the load of the weight jar assembly 44, slides down the key holder sleeve 46 to engage the lower rotator 38 and push the lower rotator 38 down so that, as shown in FIG. 9, the keys 54 are positioned below the keys 48. For this to happen, the load applied by the weight jar assembly 44 must be sufficient to overcome the biasing force of the spring (42 in FIG. 1) holding up the upper rotator 40 and the biasing force of the spring (38 in FIG. 1) holding up the lower rotator 40. The biasing force of the spring (38 in FIG. 1) holding up the lower rotator 40 and the beveled surface 62 of the upper rotator 40 again act to rotate the lower rotator 38 clockwise so that the keys 54 are aligned with the key slots 50 containing the stop pins 52. As shown in FIG. 8, this action returns the lower rotator 38 to the position where it constrains the upper ends 30 of the lifting dogs 18, thereby causing the lower ends 32 of the lifting dogs 18 to separate from the spearhead 16.

The overshot 10 can be used to connect a wireline to an article, such as an oilfield tool, either at the surface or in a borehole. The overshot 10 can be disconnected from the article by the same action used in connecting the overshot 10 to the article, as described above. The overshot 10 can be used in any drilling or wireline operation. For illustration purposes, FIG. 10 shows the overshot 10 suspended at the end of a wireline 70 in preparation for lowering the overshot 10 into a drill string 72 containing a core barrel with an inner tube assembly. The drill string 72 is disposed in a borehole 73 drilled in a subsurface formation 75. FIG. 11 shows the overshot 10 after it has engaged the inner tube assembly 12 and been retrieved to the surface with the inner tube assembly 12. A handling arm 74 holds the inner tube assembly 12 while the overshot 10 is disengaged from the inner tube assembly 12 as described above.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

1. An overshot, comprising: a sleeve; a coupling member having a latched state and an unlatched state disposed at a first end of the sleeve; and a load-responsive toggle mechanism for alternating the coupling member between the latched state and the unlatched state disposed at a second end of the sleeve.
 2. The overshot of claim 1, wherein the load-responsive mechanism comprises a first rotator for selectively engaging the coupling and a second rotator for selectively displacing and rotating the first rotator.
 3. The overshot of claim 2, wherein the load-responsive mechanism further comprises a weight member for applying a load to the second rotator that causes the second rotator to selectively displace the first rotator.
 4. The overshot of claim 3, further comprising a first spring member supporting the second rotator, and wherein the load is selected to overcome a biasing force of the first spring member.
 5. The overshot of claim 4, further comprising a second spring member supporting the first rotator, and wherein the load is selected to overcome a biasing force of second spring member.
 6. The overshot of claim 3, wherein the weight member is selectively movable relative to the sleeve to contact the second rotator and apply the load to the second rotator.
 7. The overshot of claim 3, wherein the second rotator is selectively movable relative to the sleeve to contact the weight member and receive the load from the weight member.
 8. The overshot of claim 3, further comprising a wireline connector coupled to the weight member.
 9. The overshot of claim 2, wherein the first rotator engages the coupling when the coupling is in the unlatched state and disengages from the coupling when the coupling is in the latched state.
 10. An overshot, comprising: an outer sleeve; a coupling member disposed at a first end of the outer sleeve; a first rotator disposed within the outer sleeve and configured to alternately engage and disengage from the coupling member, thereby toggling the coupling member between an unlatched state and a latched state; and a second rotator disposed within the outer sleeve and configured to selectively displace and rotate the first rotator in response to an applied load; and a weight member disposed at a second end of the outer sleeve for applying a load to the second rotator.
 11. The overshot of claim 10, further comprising an inner sleeve disposed within the outer sleeve.
 12. The overshot of claim 11, wherein the inner sleeve comprises a plurality of keys and the first rotator comprises a plurality of keys, and wherein the keys on the inner sleeve and the keys on the first rotator selectively come into contact to rotate the first rotator relative to the inner sleeve.
 13. The overshot of claim 11, further comprising a mechanism for selectively locking the first rotator to the inner sleeve.
 14. The overshot of claim 13, wherein the mechanism comprises a plurality of key slots on one of the inner sleeve and first rotator and a plurality of keys on the other of the inner sleeve and first rotator.
 15. The overshot of claim 13, wherein the mechanism further comprises at least one stop member coupled to the inner sleeve for selectively restricting motion of the first rotator.
 16. The overshot of claim 10, wherein the coupling member comprises a pair of lifting dogs pivotally mounted on an axle.
 17. The overshot of claim 16, wherein each of the lifting dogs has a first end for selectively engaging an article and a second end for selectively engaging the first rotator.
 18. The overshot of claim 17, wherein the coupling member further comprises a spring disposed between the second ends of the lifting dogs for biasing the second ends in opposing directions.
 19. The overshot of claim 10, further comprising a wireline connector coupled to the weight member for coupling the weight member to a wireline.
 20. A method of connecting or disconnecting a wireline from an article, comprising: providing an overshot comprising a sleeve, a coupling member having a latched state and an unlatched state disposed at a first end of the sleeve, and a load-responsive mechanism for alternating the coupling member between the latched state and the unlatched state disposed at a second end of the sleeve; coupling a wireline to the load-responsive mechanism; aligning the article with the coupling member; and selectively activating the load-responsive mechanism to alternate the coupling member between the latched state where it engages the article and the unlatched state where it disengages from the article.
 21. The method of claim 20, wherein activating the load-responsive mechanism comprises applying or releasing tension from the wireline.
 22. The method of claim 20, wherein activating the load-responsive mechanism comprises moving the overshot upwardly. 